# All Questions

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### Question about some engineering solutions in control moment gyro ECP Model 750

My attention was drawn to this design of the control moment gyroscope: Model 750 Control Moment Gyroscope. Fact sheet. Next I will give a picture from this document: This gyroscope consists of a base,...
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1 vote
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### Most likely trajectory of the Gravity Probe A spacecraft, and location of the microwave maser receiver on Earth?

Background/motivation @PM2Ring's comment under an answer to "Is there a wavelength shift between sunlight observed from the ISS versus from Earth's surface?" in Physics SE links to the ...
• 148k
421 views

### Diagonal ice tunneling rover to reach a safe pressure in Mars?

Is the ice on Mars deep enough to bore down into it to sustain around 10 PSI (69 kPa) air pressure? The device I have in mind is a rover with a reactor that melts through the ice slowly to create a ...
1 vote
50 views

### How to find the velocity vector of a planet in orbit argument of periapsis or longitude of the ascending node?

For a personal project, I am creating a fictional planet using as much actual science as possible. As the title suggests, I only have three of the orbital elements and wish to calculate the velocity ...
445 views

### Rocket Nozzle Shape and Length

How is the efficiency of a particular nozzle shape with a given length calculated? To clarify what I'm not asking for: I understand the idea behind the de Laval nozzle, where you constrict the flow ...
• 642
1 vote
59 views

### How are solid rocket propellants stored?

Unlike Liquid Propellants, solid propellants are already mixed with each other. I've always wondered, does that propellant ever go "bad"? and if it does, how do they prevent it from doing so?...
50 views

### Why can't we smash asteroids into Mars so it will move closer to the sun for colonization of the planet

It would take a concerted effort to make this happen.
39 views

### Accuracy of MRO ephemeris

I am trying to understand if I pick a point on the Martian surface, say the Airy-0 Crater, with what accuracy can I predict the earth time the MRO will pass directly overhead? It's my understanding ...
114 views

### Orbital Mechanics code not working [closed]

I'm trying to make a code that will simulate the orbit of a satellite around the moon with the Earth as the reference frame. I'm struggling because whenever I plot the variation of the orbital ...
• 27
96 views

### Was the July 29th EVA cancelled?

I no longer see the announcement of the July 29th EVA on Nasa TV's website. Was this cancelled and if so, why?
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59 views
+100

### Are there any plans to carry out more parallax observations using New-Horizons?

In 2020, New Horizons famously carried out observations of Proxima Centauri and Wolf 359 as part of an experiment to observe the parallax difference between Earth and the spacecraft. Are there any ...
• 3,093
82 views

### How much energy is used for a Starship launch? [duplicate]

I want to understand how Earth will support the thousands of Starships Musk envisions. I'm talking about the energy expended in all launch-related processes: propellant generation, transportation, ...
122 views

2k views

### Reducing required length of a mass driver using loop?

If you had a loop of electromagnets with an encapsulated payload inside vacuum tubes, how fast could you accelerate the capsule to before it reached some maximum velocity? What effect would scale have ...
51 views

### GMAT Lambert problem

I would like to plan a mission in GMAT to a certain asteroid, whose orbit and SPK file I have added in GMAT. However, I don't know how to solve the Lambert problem in it to first find the intersection ...
163 views

### What does Paul Birch mean by kg * s^-1 * kg^-1?

In Paul Birch's paper, Terraforming Venus Quickly he mentions a unit kg * s^-1 * kg^-1, which I interpreted as ($\frac{kg}{kg \cdot s} = \frac{1}{s}$). This is a valid unit, representing a rate. ...
• 5,906
1k views

### Is the set of software and hardware of modern attitude control systems exhaustive?

In the book ADCS - Spacecraft Attitude Determination and Control on page 426 there is a diagram of the JWST ACS. Next I attach a reproduction of it from the book. The diagram shows the main soft- and ...
• 297
111 views

### Satellite slew rate with respect to a ground station

For a given satellite orbit and observation time, I have the vectors containing the elevation and azimuth angles of the satellite with respect to a ground station. I know that the elevation slew rate ...
523 views

### Has Blue Origin carried out any flight or landing tests of the New Glenn first stage?

New Glenn is scheduled to launch the EscaPADE probe to Mars in the September launch window. I've read a lot about ground systems testing and prospective BE-4 static fire tests, but can't find ...
• 3,093
4k views

### How do cables and cooling lines transverse the pressure hull of the International Space Station?

The International Space Station (ISS) is notable for having large amount of unpressurized equipments on its Integrated Truss Structure (ITS), including the solar panels and the radiators. The electric ...
• 1,138
181 views

### What caused the LOX leak on Falcon 9?

On July 11, 2024, the second stage of the Falcon 9 had a LOX (Liquid Oxygen) leak in the second stage and it couldn't perform SES-2 (the second upper stage burn), causing the Starlinks onboard to be ...
• 3,796
2k views

### Can Falcon Heavy be used as a temporary replacement for the Falcon 9?

Due to an anomaly with the second relight of the Merlin engine on a Falcon 9 Starlink mission, the FAA has grounded the falcon 9 and will conduct a mishap investigation. Can falcon heavy be used as a ...
• 5,906
290 views

### Why don't rocket engines use heat tiles on the inside?

I asked in chat about rocket engines not melting @ 3300°C despite steel melting at 1400°C. The two excellent answers were: thermal mass was one answer the propellants are often piped through tiny ...
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2k views

### How do satellite trackers work when showing a "satellite"?

There are multiple sat trackers online where you can follow spacecraft orbiting Earth such as the ISS or the HST. I wonder how those trackers actually work when showing something near Earth, as the ...
93 views

### What's the numeral name of the recently launched Starlink satellites and where can I track them?

I'd like to track the recently launched Starlink sats that reached a too low orbit due to the Falcon 9 second stage leak and MVac Engine RUD. For some reason, if I wanna enter "Launch 11 July ...
188 views

### Why did Starship lose an engine on IFT-4?

By T+0:00:06 at the latest, the Super Heavy carrying Starship for Integrated Flight Test 4 appears to have lost an engine (source and image). I know it's not a huge deal, as they can complete missions ...
• 3,796
2k views

### Has a rocket engine ever been reused by a second/third stage

While rockets are basically minimal fuel tanks*, engines are steel monsters that aught to both weight much and be expensive to manufacture**. Has there ever been tried discarding the depleted fuel ...
• 599
154 views

### What are the tradeoffs in propellant choices for ion/electric based engines?

I'm under the vague impression that ion engines can use most things for propellant. What are the trade offs that influence selection, with an eye specifically towards oxygen? (Interested in the ...
• 1,114
184 views

### Would it be possible to create a relatively permanent Kessler syndrome event in interplanetary space between Earth and Venus?

A lot of interplanetary space infrastructure would be focused around Lagrange points, where collision energies would be very low. The threat in this case would come from everything traveling between ...
• 33
78 views

### Does the size of a black hole increase with mass? [closed]

I understand that extremely minute black holes can have a lot of mass. For example, A Black hole with a 120 pm radius, like a Hydrogen atom, would have a mass of 3.73x10^67 kg. Is this mass already ...
208 views

### Are there any video/audio recordings of the launch of sputnik 1?

I've been researching the launch of sputnik 1, it is often renowned as the event that started the space age though I cannot find any confirmed videos of the launch or even a countdown/audio recording ...
135 views

### What's the theoretical dV of the SNAP-10A satellite?

SNAP-10A, launched in 1965, was the first nuclear reactor tested in orbit. It was intended to produce 500 watts of electricity for a year, but it only lasted 43 days; a voltage regulator in the ...
122 views

### Is it possible to easily change the inclination when using momentum exchange tethers?

Access to space using Momentum exchange tether (like Skyhook, Space elevator,...) is economical, but only to specific orbits. And changing the inclination of the orbit is very uneconomical. Is there ...
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194 views

### Does an interplanetary trajectory exist to escape the Solar System and impact the Sun "simultaneously"?

This question is inspired by Do you need 0 km/s velocity to crash into the sun? which brings up the peculiarity (at least to the layman) of Solar System escape from 1 AU taking less $\Delta V$ than a ...
157 views

### Is perceived weightlessness greater in orbit due to constantly falling?

I'm familiar with $F_{g} = G\frac{m_{1}m_{2}}{r^{2}}$ and I was wondering if that means anyone orbiting the Earth actually experiences greater perceived weightlessness due to orbit itself compared to ...
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1k views

### Does it make sense to use a skyhook to launch and deorbit mega-satellite constellations now?

One issue with sky hooks is that to keep them spinning, they need to accelerate and decelerate the same amount of mass; otherwise, they would change their velocity and might even slow down so much ...
• 5,906
57 views

### Technical Question on Ignition Back Pressure

I am looking for understanding the backpressure or pressure stabilization of the injector inlet of the engines, during ignition (T-0). Are there books or papers that you suggest to check for ...
• 111
182 views

### Open air dock to space in a rotating space station?

Suppose you had a very large pipe, say 20 meters in diameter, open to space at the hub of a spinning station, and leading off radially from the hub towards the rim, where the pipe is sealed. After ...
396 views

### TWR of near-term NTR engines

With DRACO aiming for on-orbit demonstration of nuclear thermal rocket propulsion (NTR) in 2027, it seems like a technology that has had on-and-off interest for the last 70 years might finally become ...
• 642
108 views

### Could there be a difference to the human body between Low Earth Orbit “zero G” microgravity and midway between planets weak gravitational fields?

Would there be different effects on the human body (physiology, chemistry, psychology, other) over long periods of time if there was very very low gravitational field acting on it instead of being in ...
• 3,438
1 vote
372 views

### If the Van Allen Radiation Belt reaches temperatures of 35,000C, How is it possible to go through them when the craft has a boiling point of 4000C? [closed]

Van Allen Radiation Belt = 35,000C Boiling point of carbon fiber = 4200C Boiling point of Aluminum = 2470C
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1k views

### Are all Starship/Super Heavy "cylinders" 4mm thick?

Source The bodies of both rocket stages are made from stainless steel[18] and are manufactured by stacking and welding stainless steel cylinders.[19] These cylinders have a diameter of 9 m (30 ft) a ...
95 views

### Is Starship monocoqué?

Does Starship have any internal bracing to support it? Or is it a "balloon tank" relying on tank pressure to stand?
127 views

### What is the dark brown gas emission seen during the ascent of Starship?

During the video (see below) of Starship IFT-4 there is a lot of brown smoke or gas in the Superheavy exhaust from near the start for almost 30 seconds. Is this NO2? If so roughly how much is produced?...
• 9,800
78 views

### How much propellent is vaporized to pressurize the Starship and Super Heavy tanks?

We know they use autogenous pressurization. But how much methane and oxygen is vaporised to do this? I would like a figure for each of the 8 individual tanks in the stack. TBH I'm trying to figure out ...
37 views

### Does increased thermal emissivity decrease the effectiveness of a solar sail?

I am aware that increased emissivity in solar sails aids with heat reduction, however, I have done some research and found that the emissivity decreases the trajectory of the solar sail through the ...
1 vote
38 views

### Interpreting phasing maneuver results using electric propulsion in GMAT

I'm trying to simulate an anomaly phasing maneuver in three different scenarios using electric propulsion in GMAT. The idea is to use the altitude difference (of ~7-8km) between two spacecrafts to ...
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978 views

### What is the value of air anisotropy?

I am calculating a jet - gas nozzle and to calculate it, I need to know the anisotropy of the air, what is it equal to? In this formula, the desired value is under the letter ...
65 views

### How does a Space-Stabilized Inertial Navigation System actually torque its gimbals?

I've been trying to make a fairly-accurate video (with 3D animations coming soon) about Inertial Navigation Systems (INS), in which I plan to cover all the details from each gyroscopes and ...